Preheaters for revolving tubular kilns



Nov. 8, 1966 w. KRAMER PREHEATERS FOR REVOLVING TUBULAR KILNS 2 Sheets-Sheet 1 Filed Feb. 13, 1964 Nov. 8, 1966 w. KRAMER PREHEATERS FOR REVOLVING TUBULAR KILNS 2 Sheets-Sheet 2 Filed Feb. 13, 1964 ii; ZN?

inven/on- WAL Mex/01mm United States Patent C 3,284,072 PREHEATERS FOR REVOLVING TUBULAR KILNS Walter Kramer, Frankfurt am Main, Germany, assignor to Fellner & Ziegler G.m.b.H., Frankfurt am Main, Germany Filed Feb. 13, 1964, Ser. No. 344,701 Claims priority, application Germany, Feb. 16, 1963, F 39,035 5 Claims. (Cl. 263-32) The present invention relates to improvements in revolving tubular kilns and is particularly concerned with preheaters utilizing the exhaust gases from such kilns or furnaces.

For burning cement, magnesite, lime or the like, revolving tubular kilns are used to a great extent. Inasmuch as the exhaust gases of such revolving tubular kilns leave the kiln at a relatively high temperature at the entrance for the material to be burned, the operation of such a revolving kiln causes considerable exhaust gas heat losses. In order to eliminate these exhaust gas heat losses as much as possible such revolving kilns are connected to exhaust gas heat exchangers. Thus there are exhaust heat gas utilization devices which are rotatable and which are in the form of drums that can be connected in the exhaust stream and which have a wall through which the gas can penetrate. These drums are more or less filled up with rings; Exhaust gas utilizers of this type are, however, only usable for the elutriating process.

Where the dry process is employed, traveling grates, suspension gas exchangers and the turbulent flow method have been utilized successfully as far as heat economy is concerned. This involves heat exchangers in which the granulated or pulverized raw material is brought into immediate contact with the exhaust gases of the revolving tubular kiln, if necessary with the aid of cyclones or the like.

Heat exchangers provided for the dry process must frequently be of considerable structural height and also require additional mechanical means, so that the utilization of the exhaust gases introduces expensive construction as a requisite.

It is an object of the invention to provide a shaft preheater for a rotary kiln installation which is efiicient from the standpoint of heat utilization. The structural height of this installation can be considerably lower than was normally the case heretofore. parts are to be limited to the minimum. In addition, it is an essential object of the invention to construct the shaft preheater in such a manner that the material layers of the shaft preheater are relieved to a great extent of dust particles which develop already either during the feeding of the material in the shaft preheater or are carried along by the exhaust gases of the revolving tubular kiln.

In order to solve these problems the invention provides a shaft preheater for the material to be burned which has a gas shaft and a material shaft alongside one another. The exhaust gases of the revolving tubular kiln penetrate the layers of material in the material shaft twice transversely with respect to the material layer with the aid of a ventilator system.

In such a known arrangement of the shaft preheater for a revolving tubular kiln the invention provides, first of all, that the exhaust gases after penetrating the material layer in the lower part of the shaft preheater are first purified in a dust separating device and then are supplied by way of the ventilator system to the material layer in the upper part of the shaft preheater.

In a preferred embodiment of the invention this burning installation is constructed in such a manner that the Movable mechanical exhaust gases of the revolving or rotary kiln are supplied directly to a central gas shaft which is subdivided by a fire wall or iron wall into an upper and a lower part of the shaft preheater. Alongside of this gas shaft at least one shaft is provided for treating the material. The separating wall or walls between the gas shaft and the material shaft or material shafts are constructed in a known manner to permit the penetration of the gas. At the outer walls of the material shaft or shafts gas withdrawing hoods of the ventilator dust separating system are connected in the lower part of the shaft preheater, and conduit means are provided which lead from this ventilator dust separating means to the gas connecting hoods that join the outer walls of the upper part of the shaft preheater.

Such a shaft preheating installation which operates in combination with a revolving or rotary kiln provides essential advantages over shaft preheaters and other preheating installations known heretofore. The exhaust gases of the revolving kiln penetrate first the lower part of the material layer of the shaft preheater. The exhaust gases are withdrawn by suction from the revolving kiln through the material layer of the shaft preheater by means of a ventilator system which is connected to the outside of the shaft preheater. In this manner the exhaust gases are immediately conducted to a dust separator after they have penetrated the material layer of the lower part of the shaft preheater. The dust components of the exhaust gases of the kiln as well as also any dust components from the material layer in the lower part of the shaft preheater are thus separated by this dust separator from the shaft preheater. It should be particularly noted that the cleaned or purified exhaust gases of the kiln are conducted from this dust separator to the upper part of the shaft preheater. Thus there is not, as is the case in the known installations, any loading of the upper part of the shaft preheater with dust particles of the exhaust gases of the lower part of the preheater, but purified exhaust gases of the kiln are conducted through the upper part of the preheater and are especially suitable to carry along any dust components that might be encountered in the material layer of the upper part of the shaft preheater.

In structures known heretofore a ventilator was provided which was disposed in the gas shaft proper and which drew the exhaust gases of the rotary kiln out of the lower part of the shaft preheater but which simultaneously forced these exhaust gases through the material layer of the upper part of the shaft preheater. This ventilator provided in the interior of the gas shaft is subject to heavy wear due to the severe operating conditions. On the other hand, the ventilators provided in accordance with the invention on the outside of the material shaft are considerably more reliable in operation and due to the intercalation of the dust separator, also the wear of the ventilators that are provided on the outside of the shaft is reduced considerably.

In a preferred embodiment of the invention the shaft preheater is of rectangular cross section. Advantageously one each material treating shaft is provided at least at two oppositely disposed walls of the gas shaft.

It is made possible by these measures to economize with respect to the height of the shaft preheater. Instead the shaft preheater may be correspondingly long in its rectangular cross section. It will also be possible in this connection to have the thickness of the material layers only of such a dimension that the withdrawing of the exhaust gases by suction through these material layers is effected with rather tolerable power consumption by the ventilator system. The gas shaft above the separating wall in the region of the upper part of the shaft preheater can be provided at its upper end with a ventilator '3 suction means. This ventilator is not subjected in that location to unreasonable loads because in the upper part of the upper portion of the shaft preheater the exhaust gases are already cooled considerably and also because practically dust-free exhaust gases are led out.

Further objects and advantages of the invention which concern the construction of the walls of the material shafts or hot gas shafts, the material feeding means and the discharge means connected to the material shafts will become apparent from the embodiment of the invention illustrated in the drawings, in which:

FIG. 1 is a partial longitudinal section of a shaft preheater with the intake of the connecting revolving tubular kiln,

FIG. 2 is a cross-section of the kiln taken along line 2-2 in FIG. 1, and

FIG. 3 shows the cyclone separator system for the gases to be discharged.

The shaft preheater consists of a gas shaft 1 and the two adjacent material shafts 2 and 3. As shown in FIG. 2, the gas shaft as well as the two adjacent material shafts are of rectangular cross-section. The dimensions of this shaft structure including the gas shaft 1 and the two material shaft 2, 3 may advantageously be of a crosssection of 1.20 m. x 1.20 m. and of a height of about 6 m.

The preheater of the shaft is connected by means of the transfer shaft or section 4 with the intake end of the revolving tubular kiln 5. The material to be treated is fed to the two charging devices 6, 7 in the form of raw powder. The charging devices are in the form of granulating plates. These granulating plates are disposed at an acute angle with respect to a horizontal plane. By feeding water to the granulating plates the raw powder is granulated and fed in the granulated condition to the shaking channels 8, 8a. Material that is not sulficiently granulated or powdery components are screened out in the shaking channels 8, 8a, the bottom surfaces of which are in the form of screens. The separated raw components are then returned by way of funnels 9, 9a to the supply of raw powder or to the granulating plates.

The raw material which is sufficiently granulated is fed by the shaking channels 8, 8a to the conveyor belts 10, 10a. The raw granulations are then supplied by the conveyors 10, 10a to the overflow funnels 11, 11a. The angular position of the bottom surfaces 12, 12a of the funnels 11a may be made adjustable relative to the horizontal. Actuating means may be provided for the bottom surface members 12, 12a or for the entire funnels 11, 11a which control the inclination of these funnels or of these bottom surface members in a continuous fashion.

As mentioned above, it is the purpose of such a charging device to deliver the granulated raw materialy gently into the shafts 2, 3 for the material to be burned. The granulations formed on the granulating plates 6, 7 should be introduced into the material shaft as cautiously as possible so that in the shaft proper no additional formation of powder need be expected which could impede the passage of the exhaust gas. It is also possible, for example, to make the bottom surface members 12, 12a of the funnels 11, 11a in the form of conveyors that are reciprocably movable by suitable drive means in the direction of the longitudinal axes of the shafts 2 and 3.

The overflow funnels 11, 11a can be covered up to the overfiow housings 13, 13a with housing covers 14, 14a in order to encase the entire material supply means from the granulating plates to the upper intake ends of the material shafts 2 and 3 in a dust-proof manner.

Nozzle housings 16, 16a and 17, 17a are connected to the outer walls 15, a of the two material shafts 2 and 3. These nozzle housings are connected by way of conduits 18, 18a and 19, 19a with ventilators 20, 20a as shown in FIGS. 1 and 2 of the drawings. Cyclone suction dust separators 21, 21a are interposed in these ventilator assemblies. The raw powder dust which is 4 separated here is conducted by way of conduits 22, 22a back to the fresh raw powder. The conduits 18, 18a, and the cyclones 21, 21a seen in FIG. 2 are not visible in FIG. 1 because they are located behind the conduits 19, 19a.

In the gas space 1 a transverse wall 23 is provided. The exhaust gas from the revolving kiln 5 arrives by way of the passage 4 in the space of the gas shaft 1 which is limited at the top by the transverse wall 23. The outer walls 15, 15a and the inner walls 24, 24a of the gas shaft or of the material shafts are provided with slots in order to permit the passage of gas.

The exhaust gas which enters the lower space of the gas shaft 1 is drawn by the low pressure produced in the nozzle members 16, 1611 through the slots 25, 25a of the walls of the gas shaft transversely through the layer of material in the material shafts 2 and 3, thence into the slots 26, 26a. After cleaning in the cyclone separators 21, 21a, the same exhaust gas is then forced by way of the ventilator system 20, 20a and the conduits 27, 27a and nozzle housing members 17, 17a into the upper part of the material shafts 2 and 3 through the slots 28, 28a for the second time throughthe material layer and thence through the slots 29, 29a into the upper part 30 of the gas shaft. Here the gas after having been extensively cooled can leave the shaft preheater through a second ventilator system 31 having cyclone separators 32 (FIG. 3) at the upper end of the upper space '30 of the gas shaft and through the passage 33.

The slots 25, 25a, 26, 26a, 28, 28a and 29, 29a in the walls of the shaft preheater are oblique and downwardly disposed in the direction of the material being treated in the material shaft. These slots may be disposed at different angular positions, or slots 26, 26a and slots 29, 29a may be inclined more than the other slots. In this manner it is to beprevented that the subnormal pressure can cause additional material components to be drawn into the ventilator system.

At the lower end of the material shafts 2 and 3 discharging means are provided for the shafts. In the pres ent embodiment each material shaft 2, 3 has four plunger devices. A single plunger 34 is shown in FIG. 1 at the left. This plunger is located in a suitable recess of the wall of the shaft preheater. The plunger is in inclined position and operates in the direction of the inclined surface 35. The discharge end of this surface 35 is also provided with an upwardly directed ledge 36. When the plunger 34 is idle, this ledge in connection with the inclined surface 35 prevents the material present in shafts 2 and 3 from being suddenly discharged downwardly. The plungers 34 are operated by drive means (not shown) in a manner that the four plungers of each material shaft operate in cadence. In this manner care is taken that the material in the material shaft is evenly delivered over the entire length of this shaft. The quantity of material leaving the shaft at any time thus is kept in balance with the quantity of raw material which has been supplied in granulated form through the feeding means for the material shafts described hereinabove.

The arrangement chosen for the gas shaft as well as for the material shafts and the form of their separating walls insures that the type of gas discharge provided in accordance with the invention is repeatedly passed through the bed of material and that the heat of the exhaust gases is economically utilized.

The arrangement of the few mechanical means for this shaft preheater is such that they are as remote as possible from the heat effect and can be properly observed by the operating personnel. The likelihood of failure is thus greatly reduced.

Having now described my invention with reference to the embodiment illustrated in the drawings, I do not wish to be limited thereto, but what I desire to protect by Letters Patent of the United States is set forth in the appended claims.

I claim: I

1. Method of treating material such as cement, magnesite, lime and the like prior to burning in a revolving furnace or kiln in a shaft preheater having adjacent generally vertical gas and material shafts, said method comprising the steps of drawing the exhaust gases upwardly into the lower portion of the exhaust gas shaft of the preheater, then directing said gases transversely through the material in the lower portion of a material shaft in the preheater, cleaning the exhaust gases upon passing through the material in a dust separator, and then forcing the gases by ventilator means upwardly and then transversely through the material layer in the upper portion of the material shaft of the preheater and into the upper portion of the exhaust gas shaft.

2. Apparatus for treating material such as cement, magnesite, lime or the like prior to burning in a rotary furnace or kiln, said apparatus comprising, in combination, a rotary furnace, a preheater having a discharging and exhaust shaft connected to the rotary furnace for receiving exhaust gases from and for supplying pretreated material to the furnace, a center gas shaft arranged above said discharging and exhaust shaft, said center gas shaft having a transverse wall dividing said gas shaft into an upper and a lower portion, at least one material shaft disposed adjacent said gas shaft, said material shaft being defined between a first wall separating the material shaft from said gas shaft and a second wall, said first and second walls having passageways for gas, an intake nozzle for drawing gas through material in the lower portion of said preheater mounted on said second wall, a ventilator dust separator connected to said nozzle, and a circulating nozzle connected to said second wall in an area higher than said intake nozzle substantially at the level of said upper portion and duct means connecting said ventilator dust separator and said circulating nozzle.

3. Apparatus for treating material such as cement, magnesite, lime or the like prior to burning in a rotary furnace or kiln, said apparatus comprising, in combination, a rotary furnace, a preheater having a discharging and exhaust shaft connected to the rotary furnace for receiving exhaust gases from and for supplying pretreated material to the furnace, a center gas shaft arranged above said discharging and exhaust shaft, said center gas shaft having a transverse wall dividing said gas shaft into an upper and a lower portion, at least one material shaft disposed adjacent said gas shaft, said material shaft being defined between a first wall separating the material shaft from said gas shaft and a second wall, said first and second walls having passageways for gas, an intake nozzle for drawing gas through material in the lower portion of said preheater mounted on said second wall, a ventilator dust separator connected to said nozzle, and a circulating nozzle connected to said second wall in an area higher than said intake nozzle substantially at the level of said upper portion and duct means connecting said ventilator dust separator and said circulating nozzle, said preheater being of rectangular cross-section.

4. Apparatus for treating material such as cement,

magnesite, lime or the like prior to burning in a rotary furnace or kiln, said apparatus comprising, in combination, a rotary furnace, a preheater having a discharging and exhaust shaft connected to the rotary furnace for receiving exhaust gases from and for supplying pretreated material to the furnace, a center gas shaft arranged above said discharging and exhaust shaft, said center gas shaft having a transverse Wall dividing said gas shaft into an upper and a lower portion, a pair of material shafts disposed adjacent said gas shaft, said material shafts being each defined between a first wall separating the material shaft from said gas shaft and a second wall, said first and second walls having passageways for gas, an intake nozzle for drawing gas through material in the lower portion of said preheater mounted on each said second wall, a ventilator dust separator connected to each said nozzle, and a circulating nozzle connected to each said second wall in an area higher than said intake nozzle substantially at the level of said upper portion and duct means connecting said ventilator dust separator and said circulating nozzle, said preheater being of rectangular cross section, and said material shafts being provided on two opposite sides of said gas shaft.

5. Apparatus for treating material such as cement, magnesite, lime or the like prior to burning in a rotary furnace or kiln, said apparatus comprising, in combination, a rotary furnace, a preheater having a discharging and exhaust shaft connected to the rotary furnace for receiving exhaust gases from and for supplying pretreated material to the furnace, a center gas shaft arranged above said discharging and exhaust shaft, said center gas shaft having a transverse wall dividing said gas shaft into an upper and a lower portion, a pair of material shafts disposed adjacent said gas shaft, said material shafts being each defined between a first wall separating the material shaft from said gas shaft and a second wall, said first and second walls having passageways for gas, an intake nozzle for drawing gas through material in the lower portion of said preheater mounted on each said second wall, a ventilator dust separator connected to each said nozzle, and a circulating nozzle connected to each said second wall in an area higher than said intake nozzle substantially at the level of said upper portion and duct means connecting said ventilator dust separator and said circulating nozzle, said preheater being of rectangular cross section, said material shafts being provided on two opposite sides of said gas shaft, and a draft ventilator provided at the end of said gas shaft in the upper portion of said preheater and above said separating wall.

References Cited by the Examiner UNITED STATES PATENTS 6/1960 Schaub 34-174 x 5/1963 Helming 26332 X 

1. METHOD OF TREATING MATERIAL SUCH AS CEMENT, MAGNESITE, LIME AND THE LIKE PRIOR TO BURNING IN A REVOLVING FURNACE OR KILN IN A SHAFT PREHEATER HAVING ADJACENT GENERALLY VERTICAL GAS AND MATERIAL SHAFT, SAID METHOD COMPRISING THE STEPS OF DRAWING THE EXHAUST GASES UPWARDLY INTO THE LOWER PORTION OF THE EXHAUST GAS SHAFT OF THE PREHEATER, THEN DIRECTING SAID GASES TRANSVERSELY THROUGH THE MATERIAL IN THE LOWER PORTION OF A MATERIAL SHAFT IN THE PREHEATER, CLEANING THE EXHAUST GASES UPON PASSING THROUGH THE MATERIAL IN A DUST SEPARATOR, AND THEN FORCING THE GASES BY VENTILATOR MEANS UPWARDLY AND THEN TRANSVERSELY THROUGH THE MATERIAL LAYER IN THE UPPER PORTION OF THE MATERIAL SHAFT OF THE PREHEATER AND INTO THE UPPER PORTION OF THE EXHAUST GAS SHAFT. 